Surface reactions on Si and SiO2 induced by CF+ and CF+2 from a mass-separated ion-beam system were studied with x-ray photoelectron spectroscopy. The bombardment energies were varied from 100 to 2±0.6 eV. We found that the surface reactions induced by fluorocarbon molecular ion bombardment largely depended on the molecular identity of the ion species, its degree of molecular dissociation upon impact, and the reactivity of the substrate surface. Four examples are shown to illustrate this new approach in altering reaction pathways. (1) CF+ bombardment at 2 eV: This led to molecular adsorption on both Si and SiO2and to SiFx formation on Si but little reaction with SiO2. (2) CF+/20 eV: This led to a higher probability of molecular dissociation upon impact and thereby opened the channel for CF disproportionation. The energy carried by the fragment was sufficiently high that the reaction channels with SiO2 was also opened. (3) CF+/100 eV: This resulted in efficient molecular dissociation and incorporation of atomic fragments rather deeply into the substrate. The channel for fluorocarbon formation was closed and those for SiC and SiF formation were opened. A silicon compound layer was formed on both substrates. (4) CF+2/100 eV: This resulted in molecular dissociation but the average energy per fragment was low. The channel for deep penetration was closed and most reactants were confined in the very top surface. CF disproportionation became a viable channel on both Si and SiO2 and a new channel was opened for etching SiO2 due to the availability of a sufficiently high local concentration of fluorine.
Geophysical investigation for engineering studies was carried out around Faith Academy, Marmara village, Kaduna within the basement complex of North-Western Nigeria. Six Vertical Electrical Sounding (VES) were established using Schlumberger configuration. The geoelectric section revealed five subsurface layers defined by the topsoil, which comprises humus, clay and laterite; followed by weathered layer which comprises of sandy soil, fractured layer which constitutes of coarse grain sands and gravels and fresh basement which is porphyritic granite. The resistivities and thicknesses of the topsoil range from 47 - 4212 Ωm and 2 - 5 m respectively. The weathered/fractured basement has average thickness of 42 m with resistivity ranging from 350 - 774 Ωm. The Areas found to meet the conditions of high basement resistivity and shallow depth to basement, are found to be at VES A1, A2, A3, A4 and A6. Hence, VES A1 have been found to be the competent zones within the study area, and are good for the construction of high-rise buildings, roads and bridges. VES A3, A4 and A6 are areas that do not meet the conditions for construction of a high-rise buildings. However, VES A3, A4 and A6 appears to be viable for groundwater exploration with aquifer thickness ranges between 18 - 42 m and depth ranges of 6 - 10 m, while the average depth to fresh basement is 43 m.
Background radiation involves the measure of the level of ionizing radiation present in the environment at a particular location. This research seek to generate data of the natural background radiation level of some selected Sections at Kabba College of Agriculture, using RadEye G20 survey meter. A total of 15 sections of the College were randomly selected and the background radiation dose rate of the sections were measured. The indoor dose rate ranged from (0.09 – 0.13) 𝜇Sv/yr, while the outdoor dose rate ranged from (0.07 - 0.10) 𝜇Sv/yr. The indoor annual effective dose were observed to be greater than the outdoor annual effective dose in all the College Sections measured. The lowest total annual effective dose 0.75 𝑚𝑆𝑣/𝑦𝑟 was found at the Academic staff block. The highest total annual effective dose of 1.09 𝑚𝑆𝑣/𝑦𝑟 was found at the livestock building, this might be due to the high-altitude nature of the area and the rocky materials used in the construction of the building. The highest total annual effective dose of the study area was slightly above the recommended limit of 1.0 𝑚𝑆𝑣/𝑦𝑟. The result obtained from this research may not constitute immediate health risk to the staff and student of the college
The interfacial reactions between ion beam deposited diamondlike carbon (DLC) films on ZnS were studied by x-ray photoelectron spectroscopy. The DLC films were deposited by pure C+ ion bombardment. The results were also compared with those obtained from ion beam deposited DLC on Ge. It was found that the films (2-20 nm thick) deposited with a pure C+ beam in the energy range of 20-300 eV on these two substrates always showed two carbon phases with a CIs binding energy difference of about 0.8 eV. The low binding energy carbon phase showed an average location among about 30 samples at about 284.4±O.2 eV whereas the high binding energy carbon phase showed it at 285.5±O.2 ev' Although carbon in a carbide form typically has C Is binding energy about 1 eV lower than that in graphite (284.7 eV), the observed difference of 0.9 eV in binding energies of the two carbon phases was not a consequence of one phase being metal carbide. Instead, the presence of these two phases appears to be characteristic of the DLC formed in this study. When the carbon in the overlayer was partly sputtered off and partly driven into the substrate by Ar+ bombardment, a carbide phase emerged with a binding energy of less than 283.8 eV for the germanium case whereas no C Is peak shift was observed in the ZnS case. Further, C/ZnS samples before and after the Ar+ bombardments showed Zn 3p and S 2p data not significantly different from those of ZnS without DLC deposition. Hence, when carbon atoms were anchored into ZnS by ion bombardment, any chemical bonds between the incorporated carbon atoms and the atoms in the substrate were much weaker than those in Ge. Adhesion tests indicated that 20 nm diamondHke films deposited on ZnS by C+ ion bombardment passed the conventional tape test and eraser-rubbing test, and those by carbon evaporation failed the tests. However, thick films deposited by ion plating adhered poorly on ZnS but very wen on Ge.
Surface modifications of silicon by exposure to a mass-separated, reactive ion beam of CF+ were studied by x-ray photoelectron spectroscopy. The effects of ion kinetic energy were characterized in terms of the various surface chemical states induced by the bombardment. The results showed that with an ion kinetic energy of 2 eV, which was much lower than the C–F bond energy of about 5 eV, molecular adsorption took place. At a bombardment energy of 10 eV, dissociative chemisorption was observed but the reaction was confined to the top surface with disproportionation of CF as the main route and little fluorination of silicon. With an ion energy of 100 eV, the atomic fragments generated by the CF dissociation possessed enough energy to penetrate below the silicon surface. It was found that silicon carbide and fluorosilyl species comprised the modified surface region and that fluorine atoms were situated closer to the surface than the carbon atoms of the carbide. Fluorocarbon species were minor surface reaction products. This work shows that distinct surface reactions may be chemically switched between the CF+ ion and the silicon surface as a function of the ion kinetic energy.
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